Fluids are often transported, stored, mixed and/or discharged from commercial tanks, bins or other portable containers. It is often desirable, if not mandatory, that the fluids held in such containers be agitated, mixed or blended on one or more occasions between the time they are loaded into the containers and the time they are discharged therefrom. In order to effect the desired mixing, one was historically required to open the container and insert a mixing unit. There were, however, several drawbacks to such an approach.
First, of course, if a plurality of containers were stored in close proximity, it was often difficult to gain access to the selected container in the manner required not only to remove the lid, or open the port provided, but also to insert the mixing unit. But even if the lid, or the port, was readily accessible, it was sometimes difficult to remove the lid, or open the port, particularly if the material in the container was highly volatile and the openings had been sealed to retain the vapors.
Moreover, the diameter of the access opening through which the mixing unit was required to be inserted had to be of sufficient diameter to permit the insertion of the impeller blades therethrough. In addition, if the container was substantially full, the mixing unit had to be operated with considerable care so as not to splash, or otherwise spill, the contents. This often required operating the mixing unit at those speeds, and at those power settings, which were simply not efficient for the degree to which the contents of the container should be agitated, mixed or blended.
Even in those situations where the necessary mixing could be accomplished at the speed, and power, permitted, the mixing unit had to be withdrawn and the container closed after the mixing operation was concluded. The complexity of the closing operation was compounded if the container had to be sealed to preclude either the loss of vapors or the continuous introduction of outside air.
It should also be remembered that the mixing unit would have to be completely cleaned after each usage in order to avoid contamination of the contents in the next container with which the mixing unit was to be used.
Finally, even if one were able to adapt to the aforesaid drawbacks, there is the irrefutable fact that it simply takes an inordinate amount of time to open, mix, close and seal each container let alone clean the mixing unit after each use. When one considers today's labor costs such an expenditure of time incurs a considerable increase in the cost of shipping and storing fluids which require agitation, or the like, at repeated intervals.